Power converters are used to convert electric power from one form to another, for example, to convert direct current (DC) to alternating current (AC) and vice versa. Power converters play an important role in the development of alternative energy sources which often provide power in a form that is not ideal for use or distribution. For example, photovoltaic (PV) panels installed on the roof of a building may provide power in the form of DC current at relatively low voltages. This power must be converted to AC current at higher voltages for use with lighting or appliances within the building, or for distribution to other users through the power grid. As another example, a plug-in hybrid vehicle may need to convert AC power from the grid to DC power for storage in a battery. The DC power from the battery may then need to be converted back to AC power to operate the vehicle drive train, or to feed power back to the grid if the vehicle is also used as an off-peak energy storage device. Even within energy systems based on conventional sources, power converters are becoming more important to implement advanced energy management, storage and conservation techniques.
FIG. 24 illustrates a prior art photovoltaic (PV) energy system for delivering solar energy to a utility grid. The PV array is voltage and current sensed to acquire maximum power point tracking at the panel or module level. In a solar energy/power conversion system, the inverter is a critical component which controls the flow of electricity between the PV module and the load, for example, a battery or the grid. Conventional inverters operate at higher power levels, typically from one to several hundred kilowatts peak (kWp). At these high power levels, inverters typically require heat sinks and fans or liquid cooling to accommodate higher heat dissipation. The addition of the fan and/or liquid cooling reduces the reliability of the system.